A hillock measured on a growing calcite mineral surface. Each step is a single molecular row in height (3.1 Å). The net growth rate of the crystal is determined by both the density of steps and their velocity. Imaged on a MFP-3D AFM. Scan size 6 µm. Image courtesy of Andrew Stack (ORNL) and Jacquelyn Bracco (Wright State University). For further details see: Bracco, J. N., Stack, A. G., Steefel, C. I. (2013) Environ. Sci. Technol. 47, 7555-7562.